Comparison of Costs and Benefits for DC and AC Transmission

摘要

The purpose of the study reported here was to examine generic cost differences between direct current (dc) and alternating current (ac) systems and to identify situations in which dc is clearly advantageous for long distance and bulk power transport. The study was also designed to determine the value of the dc technology when applied to transmission systems. This report presents cost comparisons between ac and dc substations and transmission lines as a function of capacity and voltage. It also presents a comparison of dc versus ac for increasing the capacity of existing corridors. Direct-current link operating stategies for enhancing the performance of the associated ac network are illustrated. Possible opportunities for simplification and cost reduction of dc converter stations are described. Both current and expected future enhancements for ac system operation are also identified to assist in making comparisons between equivalent systems. Information is presented to enable comparisons sufficiently detailed to determine ''cost break-even distance,'' which is the transmission length at which the savings in dc line costs (compared to ac) equals the additional costs of the dc converter stations (compared to ac substations). However, it is emphasized that proper use of the concept requires the inclusion of all costs of implementation of those attributes available in the two technologies which are of sufficient value to the power system to be included in determining equivalent systems. The report attempts to bring together useful cost and performance information on ac and dc power transmission for the use of electric utility system in achieving economic and reliable power system designs when considering system additions, expansions, or modifications. (ERA citation 12:024790)